This isn’t a case of fighting moral codes. This is a case of battles of safety.
There are many issues of safety that affect all people, including food safety, mental safety, economic safety. All of those have resulted in court battles, as well as court failures. Safety from violence is the basic one, and people will often need to make their decisions around it on a faster basis than courts can proceed.
That’s the practical analysis, rather than the idealistic view where every single disagreement of any kind would receive a protracted court debate with all evidence present.
People are all capable of in-the-moment vigilantism (heck, most murderers feel this way). Society can still evaluate their cases afterwards to say whether they were warranted or not. I argue people should feel some safety from repercussions if society can agree their actions demanded some form of immediacy beyond what courts could provide, and did something good for society or were necessary for their own safety.
A zealot would get no such votes unless they were given a jury of their fellow zealots, and if that’s possible then I can think of no fair justice system in such a society.